1. Field of the Invention
The present invention relates to an exercise machine.
2. Summany of the Prior Art
An enormous range of mechanical devices exists which are intended to promote physical fitness. They operate by providing resistance against which muscles can work, through the medium of weights, springs, friction, or hydraulic damping. Since the most fundamental criterion of fitness is cardio-vascular performance--the ability of the heart and lungs to support sustained physical effort--the most useful fitness machine is one which can be used to exercise, in rapid succession, every major muscle group in the body, in order to provide a sustained cardio-vascular load without over-exhausting individual muscles. It is an additional advantage if such a machine provides resistance in both directions of any given movement, so that complementary muscles are exercised simultaneously. Additionally, it is desirable for the design to be such that a user is unlikely to sustain injury as a result of inexperience, and for the machine to be as light and compact as possible.
Many exercise machines have been proposed in which one or more handles are attached to a base by a pivot assembly. The most widely used pivot assembly is a ball-and-socket joint, and examples of such exercise machines are shown in GB 832387, GB 1347694, GB 2147212, U.S. Pat. Nos. 605,747, 1,535,391, 2,909,371, 3,428,311, 4,249,727 and FR 617163. It has also been disclosed in DE 94582 to use a hook-and-eye joint. Some of these exercise machines allow relatively free movement of the handle(s) but in most of them the pivot assembly contains means for providing a frictional resistance to movement (often variable) to provide a measure of stability or support for the user in some exercise positions.
However, despite the large number of such proposals, none has found practical success. The reason for this is thought to be that the shape of the socket required to retain the ball during exercise constrains the degree of movement of the handle. This is particularly important when the machine is not simply a "fun exercise" machine to assist the user to move to a variety of positions, but is intended to be used to provide a sustained cardio-vascular load. Then a controlled freedom of movement of the handles at the pivot assembly is necessary, in association with suitable resistance to movement and this cannot be provided by a simple ball and socket joint. In any ball-and-socket joint, the provision of resistance conflicts with the freedom of movement of the ball, and in practice the ball-and-socket must either be firmly clamped in place, or can move relatively freely. It is very difficult to give resistance to movement which does not effectively clamp the ball.